(a) 100 µm - Helmholtz-Zentrum Berlin

More documents

Recommendations

Info

$Math.-Nat. - Papier - Helmholtz-Zentrum Berlin$

32 State of the art IMEC has achieved solar cell efficiencies of up to 4.5 % [61]. The influence of rapid thermal annealing (RTA) and hydrogen passivation of defects in the absorber layers is examined at IMEC in order to improve the solar cell parameters [62]. HMI focusses on the low temperature route which promises an even higher poten- tial in cost reduction than the high temperature approach. The ALILE seed layers are prepared on glass substrates limiting all process temperature to below 600 °C. It was shown that small amounts of oxygen present during Al deposition decrease the layer exchange process time, but upon further increasing the oxygen amount has the opposite effect occurs [63]. Samples are thickened epitaxially using electron cyclotron resonance chemical vapor deposition (ECRCVD) [64]. Characteri- zation of defects in low temperature epitaxy is very important and done at HMI by defect etching, electron spin resonance (ESR) and photoluminescence (PL) [65]. Both approaches are supported by electron microscopic characterization methods like transmission eleoctron microscopy (TEM), high resolution TEM (HRTEM) and electron energy loss spectroscopy (EELS) at TUW [66]. At KUL the use of other metals, e.g. Sb, for alternative crystallization concepts are studied in order to ob- tain n-doped poly-Si. Besides the activities at the UNSW and within the METEOR project, many other institutions started research in ALILE related research during the last couple of years. At Samsung in South Korea, it was found that the formation of the preferential orientation depends upon the annealing temperature; the lower the annealing temperature, the higher the preferential (100) orientation [67]. Toyota explored the use of SPC of a-Si on ALILE seed layers for solar cell appli- cations [68]. Some simulations were done to extrapolated the future goals for solar cells involving ALILE seed layers which claimed that efficiencies of about 13 % could be achieved when various solar cell parameters are improved [69]. Unfortunately, no time frame for these considerations is given. Slaoui et al. [70] in Strasbourg, France have investigated the influence of the structure of the silicon precursor on the layer exchange process. They found that
2.5 Current research involving ALILE layers 33 nanocrystalline Si (nc-Si) yields the smoothed surface of the resulting film. Using high temperature CVD they achieved epi-layers on top of ALILE seed layers with grain sizes up to 60 µm. The grain sizes were determined by defect etching of the grain boundaries [71]. At the London South Bank University, low temperature epitaxy using ECRCVD on an inverse ALILE seed layer structures is studied [72, 73]. The structural quality of the films is analyzed using electron back scatter diffraction (EBSD) and X-ray diffraction (XRD) analysis. The Academy of Science in Sofia, Bulgaria conducts experiments with different Al, Si layer sequences are conducted [74]. Also, the influence of different annealing atmospheres on the layer exchange process has been explored indicating that the use of hydrogen in the annealing atmosphere leads to improved strutural properties of the resulting poly-Si film [75]. At the Technical University München the use of the ALILE process for crystallization of amorphous SiGe is investigated. Here, it was found that ALILE is suitable for crystallizing binary amorphous material without segregating different phases [76]. The optical and electrical properties of the resulting poly-crystalline films were found to be comparable with high quality crystalline SiGe films [77]. In the USA many groups (NREL [78, 79], Caltech [80], University of Berkeley, University of Arkansas and University of Arizona) have recently started working on thin film c-Si devices either making direct use of the poly-Si layer formed by ALILE or using similar thin film seed layer concepts. At the Hahn-Meitner-Institut (HMI), where this work has been done, a group of researchers is dealing with solar cell concepts based on the ALILE process. As men- tioned before the poly-Si layers exhibits not only large grains but also a preferential (100) orientation [81]. Due to the high hole density (2 × 10 18 cm −3 [82]) ALILE poly-Si layers are not suitable as absorber layers. But both the large grain size and the preferential (100) orientation make ALILE layers eligible as templates (seed layers) for low temperature (< 600 °C) epitaxial growth of an absorber layer. At
Page 1: Nucleation and growth during the fo
Page 5: "Our ignorance is not so vast as ou
Page 9 and 10: Zusammenfassung Dünne Schichten au
Page 11: • Temperatureprofile mit hoher En
Page 14 and 15: 3.2 In-situ optical microscopy . .
Page 17 and 18: 1 Introduction ’Solar power is ho
Page 19 and 20: por deposition (PECVD) achieved par
Page 21 and 22: phous silicon interface layer is ex
Page 23 and 24: 2 State of the art This chapter giv
Page 25 and 26: 2.1 Kinetics of phase change 9 Figu
Page 27 and 28: 2.1 Kinetics of phase change 11 [e
Page 29 and 30: 2.2 Solid Phase Crystallization (SP
Page 31 and 32: 2.2 Solid Phase Crystallization (SP
Page 33 and 34: 2.3 Metal-Induced Crystallization (
Page 39 and 40: 2.4 Aluminum-Induced Layer Exchange
Page 45 and 46: 2.5 Current research involving ALIL
Page 47: 2.5 Current research involving ALIL
Page 51 and 52: 2.5 Current research involving ALIL
Page 53 and 54: 3 Experimental This thesis is focus
Page 55 and 56: 3.1 Sample preparation 39 does not
Page 57 and 58: 3.1 Sample preparation 41 � �
Page 59 and 60: 3.2 In-situ optical microscopy 43 m
Page 61 and 62: 3.2 In-situ optical microscopy 45 B
Page 63 and 64: 3.3 Electron Back Scatter Diffracti
Page 65 and 66: 4 Results In order to understand an
Page 67 and 68: 4.1 Interlayer 51 (a) (b) Figure 4.
Page 69 and 70: 4.1 Interlayer 53 Figure 4.2: TEM c
Page 71 and 72: 4.1 Interlayer 55 c o u n ts [a .u
Page 73 and 74: 4.1 Interlayer 57 R C [% ] 1 0 0 8
Page 75 and 76: 4.1 Interlayer 59 � � ��
Page 77 and 78: 4.1 Interlayer 61 � � ��
Page 79 and 80: 4.1 Interlayer 63 -2 ] N G [m m 8 6
Page 81 and 82: 4.1 Interlayer 65 TA = 450 °C TA =
Page 83 and 84: 4.1 Interlayer 67 (111) (100) (110)
Page 85 and 86: 4.1 Interlayer 69 4.1.2 Molybdenum
Page 87 and 88: 4.1 Interlayer 71 Fig. 4.17 optical
Page 89 and 90: 4.1 Interlayer 73 R C [% ] 1 0 0 8
Page 91 and 92: 4.2 Temperature profiles 75 face la
Page 93 and 94: 4.2 Temperature profiles 77 � �
Page 95 and 96: 4.2 Temperature profiles 79 R C [%
Page 97 and 98: 4.2 Temperature profiles 81 a small
Page 99 and 100:
4.2 Temperature profiles 83 � �
Page 101 and 102:
4.2 Temperature profiles 85 (a) (b)
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
4.2 Temperature profiles 91 ��
Page 109 and 110:
4.2 Temperature profiles 93 in. Thu
Page 111 and 112:
4.2 Temperature profiles 95 ��
Page 113 and 114:
5 Discussion Two of the most import
Page 115 and 116:
5.1 Definition of three crucial Si
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
5.2 The ALILE process in the phase
Page 127 and 128:
5.2 The ALILE process in the phase
Page 129 and 130:
5.3 Depletion regions in the ALILE
Page 131 and 132:
5.4 Comparison of the qualitative m
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
5.5 Preferential orientation model
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
6 Conclusions In the aluminum-induc
Page 147 and 148:
A Preferential orientation calculat
Page 149 and 150:
The area of the base of the pyramid
Page 151 and 152:
B Abbreviations, symbols and units
Page 153 and 154:
symbol unit meaning ∆G a eV activ
Page 155 and 156:
Bibliography [1] M. Rogol, S. Doi,
Page 157 and 158:
[20] R.W. Bower, R. Baron, J.W. May
Page 159 and 160:
[38] J. Jang, J.Y. Oh, S.K. Kim, Y.
Page 161 and 162:
[58] N.-P. Harder, T. Puzzer, P. Wi
Page 163 and 164:
[72] G. Ekanayake, S. Summers, and
Page 165 and 166:
[87] H.R. Philipp and E.A. Taft. An
Page 167 and 168:
list of publications journal papers
Page 169 and 170:
B. Rau, J. Klein, J. Schneider, E.
Page 171:
(2002), 87. S. Gall, M. Muske, I. S
Page 174 and 175:
tion. Special thank’s go to Dr. M
Page 176:
10/95-09/98 student electrical engi
show all

(a) 100 µm - Helmholtz-Zentrum Berlin

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?